It is particularly hot these days (which I think is good cause it kills viruses and bacteria lingering in the air). Make sure you are well ventilated, take cold showers and drink plenty of water to ease the fatigue. Try cold fruit juices in moderation. I just entered 2nd tri too and am always thirsty for cold drinks. Extra humid too, switched on both air con and fan at night. Bills, worry later. Lol. I apply medicated oil few times a day just because I want to feel that cooling menthol feeling when I start to feel agitated and sticky. Rest more, tie up your hair in a bun, wear breathable clothings and avoid fried food if you can. Hydrate yourself more ok!
It might be hormones!